Manufacture of delustred nylon filaments

ABSTRACT

POLYAMIDE FILAMENTS WHICH ARE BOTHE DELUSTRED AND RESISTANT TO ACID DYES, COMPRISING AN INTIMATE BLEND OF A SUBSTITUTED CO-POLYAMIDE HAVING COVALENTLY BOUND ANIONIC SULPHONATE GROUPS AND A POLYAMIDE, IN WHICH IS DISPERSED TITANIUM DIOXIDE PARTICLES.

United States Patent Office 3,640,942 Patented Feb. 8, 1972 US. Cl. 260-37 N 5 Claims ABSTRACT OF THE DISCLOSURE Polyamide filaments which are both delustred and resistant to acid dyes, comprising an intimate blend of a substituted co-polyamide having covalently bound anionic sulphonate groups and a polyamide, in which is dispersed titanium dioxide particles.

This invention is concerned with the manufacture of polyamide filaments delustred with titanium dioxide particles and resistant to acid dyes.

The manufacture of delustred polyamide filaments conventionally includes the step of dispersing titanium dioxide particles in the relatively fluid melt of the polyamide-forming reactants for example caprolactam and hexamethylene adipamide, the precursors of nylon 6 and nylon 66 respectively. The fluidity of the initial melt, or of the molten oligomers formed at an early stage in the polymerisation, aids the dispersion of the titanium dioxide. If the particles were added at a later stage, say when the polymerisation was near or at completion, the difficulties of obtaining a uniform dispersion would be greatly increased.

A more recent development in polyamide technology is the proposal to incorporate covalently bound anionic sulphonate groups in a substituted co-polyamide, to improve the afiinity of the filaments for basic dyes and at the same time render the filaments resistant to acid dyes. Such a process is described in US. patent specification No. 3,142,662.

However, substituted co-polyamides containing covalently bound anionic suphonate groups, that is sulphonic acid groups of their metal or ammonium salts, are not adequately delustred by the process evolved for simple polyamides. In the presence of the sulphonate ion and the fluid melt of the co-polyamide forming reactants, the titanium dioxide particles tend to flocculate, lessening their effect.

The present invention is concerned with a method of overcoming this difliculty.

According to the present invention a method of making polyamide filaments which are both delustred and resistant to acid dyes, comprises blending chips of a substituted co-polyamide containing covalently bound anionic sulphonate groups 'With chips of a polyamide containing a dispersion of titanium dioxide particles, melting the blended chips and extruding the molten blend to form filaments.

The sulphonate content of the filaments is preferably at least 60 microequivalents per gram. The acid dye resistance of the filaments may be increased by increasing the sulphonate content beyond this preferred minimum amount, but there is no advantage in practice in going beyond about 150 microequivalents per gram of filament.

Whilst the chips may be blended in any proportions so long as the sulphonate and titanium dioxide contents of the filaments are adequate and well dispersed in the filaments, the difiiculty of blending the chips is least when the chips are of approximately equal size and each of the two kinds of chips is present to the extent of at least 40% of the total 'weight of the blend. Thus the preferred ranges of concentration of sulphonate groups in the substituted co-polyamide will vary depending on the contribution of the substituted co-polyamide to the weight of the blend, as the following examples show.

(a) At 60% by weight of the blend, the substituted co-polyamide contains from to 250 microequivalents per gram, of anionic sulphonate.

(b) At 50% by weight of the blend, the substituted co-polyamide contains from to 300 microequivalents per gram, of anionic sulphonate.

(c) At 40% by weight of the blend, the substituted co-polyamide contains to 375 microequivalents pergram, of anionic sulphonate.

Equally the total titanium dioxide requirements of the filaments are contained in the complementary chips of the polyamide and the concentration of the particles therein is dictated by the weight contribution to the blend made by those chips. The complementary chips contain 1.7 times the required percentage of TiO in the filaments when those chips contribute 60 percent to the weight of the blend 2 times the percentage of TiO in the filaments when blended in equal weights with the substituted copolyamide and 2.5 times the percentage TiO in the filaments when the chips are only 40 percent weight of the blend.

The success of the present invention in overcoming the flocculation problems of the straightforward addition of titanium dioxide particles to the polymerisable antecedents of substituted co-polyamide, is due, in the main, to avoiding contact of the particles with the strongly acid sulphonic acid groups until the polymer matrix has a viscosity which hinders the gathering together of those particlesit is the viscosity of the blended polymers which reduces the opportunity for flocculation.

The molten blend of polymers is subject to a further blending by the inevitable mechanical mixing occurring in the spinning head, ensuring an adequate dispersion of the titanium dioxide particles throughout the blend.

The process in one form includes the steps of:

(i) 'Forming a molten polyamide delustred with titanium dioxide particles and extruding the polymer to form chips,

(ii) Forming a substituted co-polyamide containing sulphonate groups, and extruding it to form chips,

(iii) Blending the chips from (i) and (ii), melting them and extruding the melt to form delustred filaments which are resistant to dyeing with acid dyes.

Suitable materials which are difunctional in a polyamidepolymerisation process and carry sulphonic acid groups have been adequately disclosed in the aforesaid US. patent specification No. 3,142,662.

The invention includes delustred filaments resistant to acid dyes composed essentially of an intimate blend of a polyamide with a substituted co-polyamide having covalently bound anionic sulphonate groups, in which particles of titanium dioxide are dispersed.

The invention is illustrated in the following example in which parts and percentages are by weight.

EXAMPLE A polymerisation charge was made up to 400 parts caprolactam, 18.5 parts of sulpho-isophthalic acid, 2.72 parts of lithium carbonate, 7.1 parts hexamethylene diamine and 16 parts of water. The charge was heated for 18 hours at 260 C. during which time a viscous substituted co-polyamide was formed. The co-polyamide had a relative viscosity of 2.26 and an amine group content of 38.8 micro-equivalent/gram (meq./gm.), a carboxyl-ic acid group content of 103 meq./ gm. and a sulphonic acid group content of 180 meq./gm. The molten polymer was extruded to form rods of the co-polyamide which were cut Analysis NH2 COH, SO3H, Relative Yarn Source meq./gm. meqJgm. meqJgm. viscosity Screw extruder 33. 7 70. 7 90 2. 41 Melt-pool machine 26. 6 63. 4 90 2. 79

Samples of yarn from both sources were knitted into sock panels and severally dyed with Astrazone Blue and Solway Blue EN. The panels dyed with the basic dye Astrazone Blue were uniformly deeply coloured and there was no evidence of heterogenity in the filaments. Equally the filaments showed an excellent and uniform resistance to dyeing with the acid dye Solway Blue BN.

What is claimed is:

1. A method of making delustred polyamide filaments which are resistant to acid dyes, comprising blending chips of a first polymer consisting of a substituted co-polyamide containing covalently bound anionic sulphonate groups with chips of a second polymer different from said first consisting of a polyamide containing a dispersion of titanium dioxide particles, melting the blended chips and extruding the molten blend to form filaments.

2. A method as claimed in claim- 1 in which the sulphonate content of the filaments is at least 60 microequivalents per gram.

3. A method as claimed in claim 1 in which the sulphonate content of the filaments is at most 150 microequivalents per gram.

4. A method as claimed in claim 1 in which the chips of the co-polyamide contribute between and weight percent of the blend, the balance being the chips of the polyamide.

5. A method as claimed in claim 1 in which the sulphonate content of the substituted co-polyamide is between 100 and 375 micro-equivalents per gram.

References Cited UNITED STATES PATENTS 3,142,662 6/1964 Hulfman 26078 3,184,436 3/1965 Magat 26078 3,321,566 3/1967 Whitman 264210 3,403,200 8/1968 Randall 260-857 3,505,165 4/1970 Kubitzek 161-173 MORRIS LIEBMAN, Primary Examiner R. ZAITLEN, Assistant Examiner US. Cl. X.R. 260 7 I P0405) UN ITEDSTATES PATENT OFFICE (569 CERTIFICATE OF CORRECTION Patent'No. 3,640,942 I Dated bruary 8, 1972 Inventor) EDWARD CRAMPSEY It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

I v Col. 3, line 14, in Example, under "relative viscosity",

"2.41" should be 2.49

line 15, under "Relative viscosity", "2.79"

should be 2.71

Signed and sealed this 25th day of July 1972.

( SEAL) Attest: EDWARD M.FLETCHER, JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

